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Title 長崎県長手,鐙瀬両部落におけるバンクロフト糸状虫症の疫学的研究,特に伝搬蚊との関係について. : 2.糸状虫症の浸淫状況.

Author(s) 和田, 義人

Citation 長崎大学風土病紀要 5(3), p.136-151, 1963

Issue Date 1963-09-23

URL http://hdl.handle.net/10069/3913

Right

NAOSITE: Nagasaki University's Academic Output SITE

http://naosite.lb.nagasaki-u.ac.jp

136 長崎大学風土病紀要　第5巻　第3号136-151頁1963年9月

Epidemiology of Bancroftian Filariasis in Nagate and

Abumize Villages, Nagasaki Prefecture, Especially in

Relation to Vector Mosquitoes

2. Endemicity of filariasis*

Yoshito WADA

Department of Medical Zoology, Nagasaki University School of Medicine

(Director: Prof. N.　OMORI)

長崎県長手,鐙瀬両部落におけるバンクロフト糸状虫症の疫学的研究,特に伝搬蚊との関係について.

2.糸状虫症の浸淫状況. 和田義人,長崎大学医学部医動物学教室（主任：大森南三郎教授）

Introduction

Bancroftian filariasis is widely distributed in

southwestern parts of Shikoku Island, western

to southern parts of Kyushu, and Ryukyus.The incidence is rather low in Shikoku, while

it is fairly higher in Kyushu especially in

coastal areas and adjacent islands, and is

much higher in Ryukyus. Generally speaking,

however, the incidences become progressively

higher towards the south, although small but

highly endemic focuses are scattered in places,Omori (1962) made a review on the role of

Japanese mosquitoes in the transmission of

malayan and bancroftian filariasis, in which

he concluded that the most important vector

mosquitoes of bancroftian filariasis are C. p.

pallens in Japan and C.p. fatigans in Ryukyus

and next one only in Japan maybe Aedes togoi.

Field observations on the transmissibility of

.mosquitoes of thepipiens group have been made

^Contribution from the Research Institute

of Endemics, Nagasaki University No. 440and Contribution No. 126 from the Depart-

ment of Medical Zoology, Nagasaki Uni-

versity School of Medicine,

by the members of our Department, Oshima

(1955), Nagatomo (1961), Omori et al. (1962),

However, on the roleof Aedes togoias a vector

of the disease precise field observations have

hardly been carried out because of difficulty

to find out such community where Aedes togoi

is breeding abundantly and also filariasis is

fairly or highly endemic.

The author made a preliminary filaria

survey in coastal villages in Fukue Island to

find out some villages in one of which more

detailed investigations could be carried out on

the epidemiology of filariasis due to C. p.

pallens, and in another one of which the role

of Aedes togoi in relation to the disease couldbe made clear, In consequence he chose the

following two villages to be suitable to the

purposes.

The special features of the two villages areas follows : Nagate is very high in the

endemicity of filariasis for Nagasaki Prefec-

ture ; has as many breeding places of C. p.pallens as usually seen in highly endemic

villages; has scanty breeding places of semi-tide-water pools for Ae, togoi. Abumize is

moderate in the endemicity; has rather scanty

Endemicity of filanasis ユ37

breeding places of C. p. pattens ; has a vast

number of semi-tide-water pools on the sea-shore.

At the two villages he started since April of1961 to study on the epidemiology of filariasisin relation to the vector mosquitoes, on the

ecology and transmissibility of mosquitoes inquestion, and on the control of thedisease by

means of only controlling the vector mosquitoes.In the present paper he deals with the results

of investigations on the epidemiology of thedisease in the two villages.

Before going further, the author wishes toexpress his sincere thanks to Prof, NanzaburoOmori of the Department of Medical Zoology,

Nagasaki University School of Medicine forhis constant leadership and encouragement.Thanks are due to the member of the Depart-

ment of MedicalZoology and also to Mr. K.

Ono of Fukue City Office who were helpful

throughout the field work.

Preliminary examinations in Fukue Island

Fukue Island is the largest one of the Goto-Islands of Nagasaki Prefecture and is about

100km west off Nagasaki City. The Island isone of highly endemic areas of filariasis in

the prefecture. The villages are scatteredmostly in coastal areas around the Island.The incidences of filariasis appeared to be

varied fairly with villages.

Among the villages, six ones were chosen

for the preliminary blood examination for

filariae with the results shown in Table 1.

The blood of 20mma was taken on a slide from

the ear-lobe of persons assembled in each

village at night from9to 12 p. m. The films

on the slide were dried and stained byGiemsa's solution.

Of the six villages, the two, Nagate and

Abumize Villages, were chosen for further

examinations as mentioned above. Nagate

Village is located near seaside having only afew semi-tide-water collections on its seashore,

and no paddy fields, while many cess-pools,

ditches, and fertilizer pits suitable for the

breeding of C.p.pollens.Thevillagers are most-

ly engaged in farming growing mainly sweet

potato, and a few of them are in fishing.

Abumize is located nearer sea-coast having

long and rather wide rocky seashore with a

great number of semi-tide-water pools, while

no paddy fields, and rather fewer breeding

places of C.p. pallens because of the absorbable

sandy soil. The villagers are engaged in

agriculture and some are in fishing,

Results of filariasis survey in Nagate and

Abumize Villages

Blood examinations for filariae were made

with all persons above one year old baby

Table 1 Preliminary blood examination for microfilariae with some persons of

several villages in Fukue Island, Nagasaki Prefecture, in December,1960,

TrM1 i ~ i Main ! No. persons ' No. (#)of

VlllaSe j Topography | occupation j examined positives

Na^ate Sa1^116^ I Farming 133 I 22(16'5)

Shimosakiyama I ^^olst Farmi^ 27° 19^ 7'0)

Kamisakiyama Among hills Farming 229 27(ll.8)

Abumize Sea-coast Farming 52 4( 7.7)

Osako Foot-hill Farming 119 1( 0.8)

Aka-shima Islet Fishery 99 0( 0. 0)I

73日 Yoshito WADA

Table 2　Results of blood examinations with all persons in

Nagate and Abumize Villages,

■一一■一一一一■一:r一一一｢｡一一一■一■■一■一一一一一一一一一一一一一■一一一=一■■一一一一一一‖一一■一一一一一■一■一一一一一一一一一■一■一｢一一l一一■■一一一｢･M"｢一ー一一一一I-一一-[一一pー一~一-什一一一一仙一一一~~小一ーvillageDateNo.of

pres｡n…11Bloodtakenperperson|(mm3)｢MIcrofilariapqsitiyes-N｡.!去Abumize,/

Nagate;/

Nagate'sるLUg

LUg

ept｡196

196

196子It≡778享20

60

3｡冒子.I｢8.3

14.0

12.4

(referred to as examinations for ail persons

hereafter). The examinations for all persons

were made in Abumize in August, 1961 and in

Nagate in August, 1961 and again in September,1962 with the results as shown in Table 2.

The microfilarial incidence was moderate in

Abumize, and fairly higher in Nagate. In

Nagate Village, however, the incidence some-

what decreased in percentage in 1962, as willbe stated later,

1) Results of the survey at Nagate Village

The numbers and percentages of microfilarial

positives found in Nagate in 1961 are given by

agegroup and sexin Table3and Fig.1. Of

577 persons examined, 81 persons or 14.0#

were found positive. The incidence is rather

high for the endemic area in Nagasaki Prefec-ture in general. The percentage forthe maleis significantly higher than for the female.Higher incidence for the male has been also

reported by some authors, for instance, Oshima(1955) and Nagatomo (1961). The latter authorsupposed the reason to be due to the custom

of the youth having spent the night in groupin club houses rarely using mosquito-nets. InNagate Village, there has been no such a

custom and consequently the reason is unknownnow, but it may perhaps be due to the

difference in susceptibility or in frequency ofcontacts with infective mosquitoes between

T甜3MicrofllarialincidenceinNagateVillagebyagegroupandsex,1961,

=一一一:一=一一:二■一一一一一■一一一一一■■一一一一一一一■一■一一■一一■一一一一一■■■一■一■■一一一一一一一一一一■■一一一一■一一一一一一一一■一-一■■一一一一■一一■■一一一一■■一一一一■一一一一■一■一一一一■｢一rr一■一一一-一一一一一一一一一T■一一一一一一一.一一一■一r▼l■■rMale!Female!Total

personsexamined一一No,pod;(i更)ofresPex一ersam｢onsined一一一画て一#)o一f一一一Personsexamined亨No.(#)ofp｡sitives

2O……;≡))冒,盲o(

5(≡:3O三

110(

7(

7(る,5.9)|67|5(7.5)

18.0)I322(6.3)

!2.6)42|5(ll.9)

2.0)29:7(24.1)i

4.4)24!5(20.8)

2.2)233(13.0)

5.9)194(21.1)一き15(1

9(1

12(1

15(2

13(3

7(1

5(1:

る377る.:I.5)

�4)

.8)

�0)

1)

9)

一一一■一一■L一一一一一一一一■､一一一一一一一■一一一一一一一一一一一一一一一一一一一一一47(17.7)31234(10.9)57781(14.0)一一

Endemicity of filariasis｢つG

the sexes, as supposed by Beye et al. (1961).

The youngest positive is a girl of 6 yearsold and the oldest is a woman of 78. The

percentages of the positives vary with the age

groups becoming higher with advance in age,reaching a peak in 40-49 or50-59 age group,decreasing thereafter. The high incidences in

age groups of40-49and 50-59 may be to acertain degree due to the active infection

especially in males by the much oftenerexposure to mosquitoes by the heavy labor

even in the night-time to support their familiesfor some years just after the War. The lowerpercentages in old ages may be due to the

infection immunity.

Oral examinations for filarial symptoms weremade with the all persons in Nagate Village

in 1961. The results are given by age groupin Table 4. The persons examined are 571, of

which 59 or 10.3# are positive forsymptoms.The percentage is rather high for the endemic

area in general in Nagasaki Prefecture assame as in the case of the microfilarial

incidence. Lymphangitis is much commonand

begins with 20 or above years old. Chyluria

Fig.160#confidenceintervalsofthe

populationpercentagesforthepercentage

昔4(

5

2i

li

5

4

3｢oaP手

Table4Numberofpersonswithclinicalsignsoffilariasisbyagegroupin

NagateVillage,1961.L,C,andHmeanlymphangitis,chyluria,

andhydrocelerespectively,

■一■_一一一一一一一｢=-一一一一一一■一一■一■■=--一‖一一一一■一一一■一一一一■■一一■一一■一:■一一一一一一一一■■一一-■一一■一■一一一一一■一一一一一一一■一一一■一一一一一一一II一･ii-一一-一一一一｢■一一ー■■一■_一■■一一一ー■一一一一一一■■■一■一■一一■■一■一■■■一一一一■一■■一一一一一■一一-一■一一■■一■一一■■■一一一｢^ge

l

ooo

�0

10

.o

'｡T｢一oh-｢｢ro

ai一｢LP一一l｢,r学5S表2吉)f

nsined｢一一一｢一"一手+;4｢m-吉-芋

14o Yoshito WADA

is the least and begins with a little olderyears. Hydrocele is fairly common and begins

with a little more older years. Old villagerssay that persons having clinical signs have

been decreased in number in recent years andnow elephantiasis is scaracely observed, though

this sign has been not rarely observed severaldecades ago. This may support the opinion

that filariasis infection had been very activein the far past.

The states of endemicity of filariasis in

Nagate Village may be seen more clearly in

Fig. 2 in which are illustrated the 60^confidence intervals of population percentages

for the percentage numbers of persons by age

group belonging to the four categories in

Fig 2 60# confidence intervals of thepopulation percentages for the percentagenumbers of persons by age group belonging

to four categories combined by the occur-rence of microfilaria and symptom: M(-)S(-),M(+)S(-), M(+)S(+), andM(-)Qr_l-^ ir^ KTarratP Villao-p 1QR1

combination of occurrence (+) or absence(-)

of microfilariae (M) and symptoms (S):M(-)

S(-), M(+)S(~), M(+) S(+), and M(-) S

(+). The trend of the change in the percentage

component by age group is well demonstrated

by the curve for each category. The percentage

number of persons for both microfilariae and

symptoms negative or the percentage compon-

ent M(-) S(-) against the all persons

decreases with the advance in age till the 50

-59 age group, while thereafter it remains

roughly on the same level at a littleless than

60^, showing that more than 40^oftheseold

persons must have experienced the disease

during their life time.

From the trend of the curves for the

percentage numbers for M(+) S(-), M(+) S

(+), and M(~)S(+)> and from the relations

among them the historical changes in the

intensity of filariasis infection may be under-

standable. In this connection, in the previous

report the author tried to explain the same

subject using the triangular graph method, andcame to a conclusion that :

In recent years or 16 years after the end of

the War, especially for some years just after

the War, the living conditions of villagers

including returners were the worst and causedan active infection of the disease.

In thepast or during the War periodof

about 8 years including the China Incidence

and World War II; most males and many

females of young and middle ages having been

the highest in the microfilarial incidence moved

out from the village reducing the intensity of

infection in the home village.

In the far past or for about 50 years before

the outbreak of the China Incidence (the then

15 to 50 years old persons are now in 39 to74

ages), very active infections seem to have

been continued in the village, probably nearlyas same as in most of the filariasis endemic

villages in the prefecture,

The historical periods described above are

in

苦言1020L929一3040^w594Qb9&vし′Agし三groupn.I

Endemicity of filariasis

referred to hereafter as : Recent years orpostwar period, past years or War period,far past years or prewar period.

Now, inthe Fig, 2, thecurveforM(+) S

(-) covers evenly all over the age groups,rising in percentage, however, very slowly

towards 50-59 age group. This shows that inrecent years fairly active infection has been

taking place for persons of every age group,but more repeatedly for old age groups. Thecurve for M(+)S(+) begins at as late as 30-

39 age group becoming higher and reachesmaximumin 50-59 ages decreasing thereafter.

The very low percentage in 30-39 ages maybe due to the reduced intensity of infection

during War period to the then younger re-mainder in the village. High percentage in 50-59maybe to a certain degree due to much

oftener exposure to the mosquitoes especially inmales including returners for some years justafter the War as stated above. The progressive

rise of M (-) S (+) curve towards the olderages shows an active infection in the far past

or in the prewar period.

141

The distribution pattern of houses havingvarious numbers of microfilarial carriers in

Nagate Village is illustrated in Fig.3. In the

eastern part of the village, the incidence offilariasis is apparently higher, where collec-tions of sewage are more abundantly found

providing very favorable breeding sites of C.p. pattens. Such a distribution pattern ofpositive houses seems to have a relation to thedomestic habit of the mosquito.

The maximum and mean numbers of micro-

filariae by age group and sex in 60mm3 blood

of the positives in Nagate Village in 1961 aretabulated in Table 5, showing that the greatermean numbers of microfilariae seem to be seen

more frequently in younger or middle agegroups in both sexes. The heavily infected

ones are, however, found irrespectively of ageand sex, suggesting that in certain houses

repeated and family infections were takingplace.

The mean numbers of microfilariae of carri-

ershaving been found by ones, twos, and

threes or more in a house in Nagate are

Fig. 3 Distribution pattern of houses having various numbers of microfilarial

carriers in Nagate Village, 1961. Marks O, 0. 0, and 9 indicate

houses having 0, 1, 2, and 3 or more carriers respectively.

142 Yoshito WADA

Tab畳e 5　Maximum and mean numbers of microfilariae in 60mm^ blood of

the positives bv a巨eどroup and sex, in Nagate Village, 1961.

｢~-一子一Il~｢｢一L｢=-~｢｢==｢=｢｢1Lt

No｡ofmicrofilariae

Mean

享萱芋蔓9

9!]

9i

9;!9|

99萱j5;享22一?萱萱≡萱一⊆｢享買4+L享子亭

Total47岳5628613449478

compared in Table 6. It is apparent from thetable that the more the carriers in a house

are, the higher the microfilarial density in an

average is. An extreme example is seen in

Table 7ina family. The family has much

heavily infected carriers as many as 4 which

is the greatest for the village. These facts

imply the occurrence of the family infection

as will be examined in the following.

Frequency distributions of the number of

families having various numbers of carriers in

Table 6 Mean number of microfilariae

in 60mms blood of carriers who were found

byones, twos, andthrees or more in a

house respectively in Nagate Village, 1961.

each family size in Nagate in 1961 is shown inTable 8, There were 126 houses or families in

total, of which 53 (42^0 had or more one

carriers, i.e. 33, 13,6, and 1 houseshad1, 2,

3, and 4 carriers respectively.

If it is supposed that the filarial infection

takes place by chance, the numbers of houses

having serial numbers of carriers in each

family size will follow a binomial distribution.

Then, in Table 9, goodness-of-fit of the

Table 7 Number of microfilariae (Mf)in 60mms blood of members in a familyhaving the greatest number of carriers inNagate Village, 1961.

r一"o;ofcarriers

nahouse≡TotalNo.

｡fcarriers｣｢lea

TllC:Of｢0.O

laria三

1二三三｢-≡

｣》322一127

L一

一ITota18182一

AgeSex∫No-ofMf

=一等E,享

子442｢0

132

｡

一一49494一I

Endemicity of filariasls

T且ble 8　Frequency distribution of the number of families having theindicated

number of carriers in each family size, in Nagate Village, 1961一

二二二■⊥一一一一一一一一丁一一一一I=一一　一一一　一一■一一一一■一■　■一一-　i　一L　一一一　　一一　一■一一　一一一｢一　■■一　一一一一一一　■一二　　一一■■一=-一二二⊥一I1一一_■■一■一一一■一■一:■■一一■一一一一二二=三二二二一ニー一

size of No. of carriersin a family No. of No. of i No of

143

family

1

2

3

4

5

6

7

8

9

1O

9

13

ll

8

12

6

8

5

3

2

4

5

5

4

5

2

2

1

2　;　　3

1

0

4

2

2

2

1

1

O

33　　　　　13岳

hypothetical number of families under the

above assumption to the observed number

shown in total of Table 8 is tested. Here, the

probability in the binomial distribution or

microfilarial incidence is 14.C

Chi-squared obtained ls 5.58, which does not

show a significant departure at 5# level from

the hypothetical distribiユtion, but the proba-

bility lies between 0.05 and 0.10. This implies

that family infections are taking place though

not significantly, and that inany villages where

0

3

1

1

O

1

O

0

6

familiesト

1冒+芦

i ｡o｢

1

12

16

15

20

20

13

16

9

4

1

persons

12

32

45

8o

loo

78

112

了2

36

1O

carriers

3

4

4

22

12

Ill

13

7

4

1

81

higher microfilarial incidences than in Nagate

may be found signi臼cant family infections

should be observed as will be discussedlater.

In Nagate Village, all persons were examined

for microfilariae in August, 1961 and again in

Saptember, 1962, as already　一stated. During

the period, some persons moved as shown in

Table 10. With 540persons, whodidnot move.

the results of blood examination were compared

in Table ll. The number of persons turned

positive was 3, while the number of those

Table 9　Test of goodness･of-fit of the hypothetical number of families calculated

under the assumption of binomial distribution to the observed number

shown in total in Table 8.

No. of carriers

in a family

Observed No offamilies

Hypothetical No｡of families

0 1 1一

一

一

73　　　　33

Daviation　　　　　　　　6.29 ｢

L　　　　　　　　　-

Total

o,49　　0.06I

3.35

I

一

一

一

Ⅹ盟-test

12軍一一一X2-5.58一

126.01 I Df-2一

一一一一｡I

二｡.01 ｡O5くPく0,10

mm Yosbito WADÅ

TabIゥ柑　Movementof persons ln Nagate

Village during 1961 and 1962,

一

Subject j No. of persons

Population ln 1961　　　　　　　　　57?

Emigrated　　　　　　　　　　　　　　33

Died

lmmigrated　　　　　　　　:　　　21

一Born lC

Not moved　　　　　　　　　　　　　　　　540

Population in 1962　　　　　　　　　571

T盈b且e ll Comparison in numbers of

microfilarial positives and negatives be-

tween 1961 and 1962, in Nagate Village主⊇一=一■ ■一　　一一　　　　　　■　一一一一一一一一二■:一二二-一一　一一一一一一一一一=一一‖‖一一一一一　　　　一一一一一　　　　　　一一一一一　■　　　　　一一■一一一　一　　　　　■一　■■　　一■一一　　　一一-ll

＼--三軍61葺p｡sitives ど Negatives ㌔　T｡tal

1一962　二ゝ1一　　　　　　　　　　　L一

一

positives ;　　66　;　　　3　　j　　　69一

Negatives　　　14　　　　457　　　　471

一

Tota1　　　　80　　　　　460　　|　　540

turned negative was 14.

Furthe‡･ 1blood examination was mde in

May, 1963 with the 17 persons, 14　of which

were positive in 1961 and negative in 1962,

while the remaining 3 were negative in 1961

and positive in 1962. The numbers of micron-

lariae in them are given in Table 12｡

Because of only a haはvolume of blood being

taken in 1962, the disappearance of microfila-

riae in most of the 14 persons was doulatfui.

However, the facts that most of them were

negative for filariee in　60mm｢1 blood on the

last examination inspite of no drugs having

been administered may show the natural

disappearance of microfilariae during the

period of nineteen months during which no

transmission of the disease has been taking

place by the reason as shown in the remarks

in Table 12. The control of vector mosquitoes

were made by the residual spraying with　5#

Tab王12. Disappearance or appearanc

of microfilariae in some pei'sons durin

the observation period of 21 months.

一一一一■一一一一一一一一一一一■■■一一一一一=一=一一一一一一■■一■■一■■一一一一r一一一一一一■一■一一-r一■■一一一一一一一L一I一一一■一一一一一一■一一一一一一L一一一一一一一一一r一l一-一一一l一一一･ndてivi-uallAgef｡.一sex一No.60--3

nAug｢o:7^iin一3s長吉7lo蒜

;一19@一1一一L一一19一9一2一1963享子享…:8十;o:

喜一…32…I…一≡1≡§≡;e-igrated

｡

6一45喜o;o

87≡≡OajlO

9^9｡一Z

9一64一≡os

IO33一?

1150一?一1j00

一一1254一90一o一:11享一一し芋蔓一し',｢一一一-3芋一一一一一Ooo

emigrated

174129.一O

Remarks:Notransmissionoffilariasis

maybetakenplaceafterOctoberof1961

throughMayof1962,becauseoflowtempe-

rature,andsul)sequentcontrolofvector

mosquitoes,althoughnodrugswerebei三相

entirelyadministered.

DDTemulsiononJune6,1962andbyweekly

applicationsofDiazinonemulsiontotha

breedingplacesofC.p.pollens一Thedetailed

accountofthecontrolofvectormosquitoes

anditseffectwillbereportedinthelater

reportoftheseries,

Themlcrofilarialcountsofpositivesin1961

arecomparedwiththoseofthesamepersons

in1962inFig.4.Itisofinterestthatinmany

Endemicity of filariasis

Fig. 4　Comparison of the microfilarial

counts of the same persons between 1961

and 1962 in Nagate Village.

The line shows the same microfilarial

density between 1961 and 1962,

Sis

(∫)

e3

日ーT一一一1

｡てコ

O

(⊃▼一-｡｣

,ご〕

KI

B

∈⊂)(Yつ

(コ.,■

･トJ

ロ

コO

U

r1-一一一1

(勺一

ト

03T一-･｣

■ I-I

M-H

ohU

喜 o　　　　100　　　　200　　　　ち00　　　　　　　　　　　500

Microfilarial count in　60mm呂blood in 1961

positives the counts decreased during the

period ha.ving been kept off from the bite of

mosquitoes. In a few persons, however, the

counts somewhat increased probably bacause

145

of their being repeatedly infected shortly

before the first examination.

2) Result of the survey in Abumize Vill哨e

All persons in Abumize Village were exam-

ined for microfilariae in 1961.　The results

obtained are given by age group and sex in

Table 13. Of日4 persons examined, 7 or 8.3^

were found positive, five males and two

females. The age distribution of positives

seems somewhat different from, that in the

above mentioned village (cf. Table 3 and Fig.

1) in the point that there are few positives in

younger age groups, showing that the trans-

mission of filanasis must have been much

inactive in recent years. The reason of the

inactivity is thought to have been related to

the history of the establishment of the village.

The village, now consisting of　20　houses,

had only a few Ⅰaouses about　40　years ago.

The others were built during some　30　years

thereafter by the immigrants from nearby

villages, Kami-Sakivama and Shimo-Sakiyama■

(cf. Table 1). Therefore, almost all of the

filaria patients in the village seem to be

positive immigrants and few of them seem to

have been infected after moving in the village｡

Table 13. Microfilarial incidence in Abumize Village by age group and sex.

Age group

一

一

)

｢

Male

Persons

examined

1　-　　9　　　　　　7

一

1O　-　19　　一　　　12

糜定一■

一

一

一

一

一

ト

o. (#)ofsitivespo

0(0.0)

0(0.0)

20　-　29　　　　　　　　　　　0(0.0)一

30　-　39　一　　　　　　　　o(o.o;

一

4O　-　49　　　　　　　　　　1(16.7)一

50　　　59　　　　　　　　　　　3 (50.0)

6O　-　　　　　一　　　　2

一

一

･Tota1　　　　　　36

1 (50.0)

Female

e≡ersonsjNo.amined|p｡si至i吉)ofesF l !13…0(O.o)l ]14;1(7.1)l 一 一 0(0.0)

6､0(0.0)

10一0(0｡O)

1 (33｡3)

0(0.0)

Total

persons ! No.一(#)一両

examined ; positives

20　一　o(o.o)

26　　　　1(3.E

3　　　　　0(0.0)

了　　一　　0(0.0)

16　　　　1(6.3)

5(13.9)|　48　　2(4.2)一; 84

4 (44.4)

1 (33.3)

7(8.3)

146 Yoshito WADA

The familial aggregation of infection is

proved to be not significant. The reason is

uncertain to be due whether to the ratherlow

microfilarial incidence or to the transraissibility

of an abundant mosquito species, Aedes togoi.

Examination ofthesubjectare now in progress.

Co耶S量derat毒ons ofユ the f氣iaT盲a頁infectivity of

perso円s to mosquitoes亘T!昆common盲ty.

The frequency distribution o一I selected micro-

filarial levels in a population seems to provide

the clear picture of the occurrence of micro-

filariae as pointed out by Kessel (1957)一　Sasa

et al｡ (1959) indicated the frequency distri-

butlons against the microfilarial counts of

carriers shown in logarithmic units and Omori

+一｣

召習i.I

CH

E3I-■■1

(n

CDo

ごヒ

3感CA)O

重

し+｡｣

O

a)一÷-一｣

dト1

.岩5一i一_.)

U

A)し=

G- I.1

I一一--i

(勺J一｣

E1

眉卑ト1

U)〇1

捕

〔頁

!l

>-<

et al. (1962) in cube root units. The methods

are useful to grasp the general tendency oi

the distribution一　However, the comparison of

the results of different experiments is diffi-

cult especially in the minimum side of the

mlcrofilarial level when different amounts of

blood were taken in eac:n examination. There-

upon, the author devised a new method by

which it will be capable to compare the

frequency distributions based on the different

blood volume.

Frequency distributions are expected to be

comparable when plotted against the tentative

microfilarial levels which are set up for the

ranges of the expected infection rates　口f

mosquitoes fed on the carriers having adequate

F噛　5　Relation between the experimental infection rates in probitofmosquitoes

and the microfilarial counts in 30mm呂blood of carries in logarit士1m.

Data are from Fujisaki (1958), Om口ri (1958), and Omori(unpublished)

o ｡1b

X-Microfilarial count in 30mm呂blood in logarithm

Endemicity of filariasis 147

numbers＼ of microfilariae to get the rates.

As a procedure to gain the final comparative

illustration, the relation between the experi-

mental infection rates of mosquitoes and the

microfilarial counts in　30mm壬主blood of carriers

were examined ln Fig. 5, fromthedataof our

Department. Three forms of C. pip古ens group

seem to have similar susceptibilities, so that

all data are put together. As the relation

seems lineaトr, the regression equation is calcu-

lated as seen in the figure.

From the equation it is capable to get the

expected infection rates of mosquitoes to be

fed on carriers having various microfilarial

counts as shown in Table 14. Then, the

tentative microfilarial levels are set up for

the selected ranges of expected infection rates

as given in Table 15.

Now, the comparison was made in Fig. 6

with the frequency distributions shown in

percentage of persons being in the levels, to

the whole populations examined in different

Table 14　Microfilarial counts of carriers to be obtained for the expected

experimental infection rates of mosquitoes having been fed on

them, calculated from equation given in Fig. 5.

ExpectedInfection

rates (#) ofmosquitoes

Microfilarial counts of carriers

In lmm呂blood in20mm3blood in30mm呂blood in　60mm呂blood

･o　卜

5o

6O

7O

0.0167

O†0366

0.0641

o一1040

0.1629

0.2559

0.4140

0.7278

1.5890

0｡334

0.732

1｡2日2

2｡080

3.258

0.501

1.098

1.923

3.120

4.887

5.118　　　　　　　7.677

14.558　　　　　　　21.834

Table 15　Ranges in the integral number of microfilanal counts in carriers

to be obtained for the expected experimental infection rates of

mosquitoes shown in the given ranges or the selected levels.

Tentative

microfilarial

level

0

1

2

3

･i

Expectedinfection

rates (#)口f

m一osquitoes

O　-　20

20　-　40

40　-　60

60　-　80

日0　-

｢　　　Microfilarial counts of carriers

in 20mm王王blood

o

1 -　2

3　-　5

6　- 14

15　-

in30mm呂blood一in 60mm苫blood

O　-　1

2　-　3

4　-　7

-　21

22　-

0　-　2

3　-　6

7　- 15

16　-　43

44　-

14日 Yosnito WADA

F雑. 6　Comparison of the frequency

distribution in percentage of persons being

in tentative microfilarial levels to the total

persons examined in Nagate Village with

those in Amakubo (Nagatomo, 1961) and

Hisamatsu (Omori et al., 1962),

:-｢｢ ｢｢手｢｢_I_｢｢｢_｢｢_:-I

three villages. The frequency distributions for

Nagate and Amakuboare much similar showing

that the intensities of filariasis infection

may be nearly the same. The frequency

distribution for Hisamatsu, however, is quite

different from those for the above two villages,

The percentage for level zero is lower and that

for level 4is markedly higher. This shows that

in the last village the infection is taking place

in much more intensive grade.

The frequency distribution against the levels

is thought to represent the distribution of

filarial iniectivity of persons to mosquitoes ID

a community｡ Therefore, the averaged level

may be called an index oi filanal infectivity

of persons to mosquitoes in acommunity. The

indices are 0.38, 0.37, and l｡14　for Nagate,

Amakubo, and Hisamatsu Villages respectively

being well in line with the above statements.

The index is thought to have a close relation

to the natural infection rate of mosquitoes in

a community. The conception may be appli-

cable to the infectivity of persons in a patient s

house within a community. In Nagate Village,

natural infection rates in patient's houses are

fou王id tobe more closely related to the indices

thus obtained than to the microfilarial inci-

dences or the mean microfilarial densities in

the respective houses.

Considerations on the family抽fection

T Nagate Village where the microfilarial

incidence is 14.0#, familial aggregation of

carriers was roughly demonstrated and higher

microfilarial densities were found in houses

having more carriers. Here, it is of interest to

refer to the papers by the other authors

dealing with the same subject. In Aogashima

where microfilarial incidence was 12.｣

significant familial aggregation of carriers was

found (Hayashi, et al=1959), while ln Amakubc

Village where the incidence was as high as

17.2#

Endemicity of filariasis 149

in August of 1961, 81 or 14.0% were foundpositive. The male is significantly higher in

the incidence than the female. The percentagepositives is low in 5-9 ages, becoming higherwith age, reaching a peak in 40-49 and 50-59

ages, and decreasing thereafter. All the 571persons were examined orally for filarial

symtoms and 59 or 10.3% were found positivefor any filarial symptoms. Lymphangitis beginsin 20-29 ages and is the commonest, chyluriain a little older ages and the least, and

hydrocele in a little more older ages and fairlycommon,

The states of filarial endemicity were exa-

mined through the trend of the curves for thepercentage numbers of persons belonging to the

four categories by age group : M(-)S(-), M(+)S(-), M(+)S(+), and M(-)S(+). TheM(-)S(-) curve falls with the advance in age

till the 50-59 ages, remaining thereafterroughly on a level a little less than 60%,showing that more than 40% of villagers have

to experience the disease in their life time.The M(+)S(-) curve covers evenly all over

the age groups, increasing very slowly towards

50-59 age group, showing that in recent yearsfairly active infection has been taking place.The M(+)S(+) curve begins at 30-39 ages

with a very low percentage showing thereduced intensity of infection during the ChinaIncidence and World War II for the then

younger remainder in the village, and rises in50-59 ages probably owing to much oftenerexposure to mosquitoes especially in males

including returners for some years just afterthe War. The M(-)S(+) curve progressivelyrises towards the older ages showing an active

infection for some 50 years before the outbreakof the China Incidence.

The houses having microfilarial carriers aredistributed more concentrately in the eastern

part of the village, where are found many

collections of sewage suitable for the breedingof C.p. pallens.

Greater mean numbers of microfilariae are

roughly seen in younger or middle age groups.However, heavily infected individuals are

found irrespectively of age and sex. The meannumber of microfilariae is found greater incarriers who are found in a greater number in

a house, In this village a familial aggregationof carriers is roughly proved though not

significantly.

In the blood of some 14% of carriers, micro-

filariae disappeared naturally, during nineteenmonths from October, 1961 to May, 1963, duringwhich in cold months from October to May

the female mosquito became dormant and in

hot season from June to September mosquitoeswere controlled by residual spraying andlarvicide.

2) Abumize Village:The village is situated near seashore and

has a vast number of semi-tide-water pools

suitable for the breeding of Aedes togoi in the

long and wide sea coast.The village, now of 20 houses, had only

some 5 houses about 40 years ago, becoming

larger little by little in number of houses by10 years ago. Of all 84 villagers examined in1961, 7 or 8.3% were found positive. In younger

age groups, however, few positives weredetected suggesting little infections might have

been taking place after their immigration. Theadult carriers seem to be positive immigrants

from nearby villages.

3) The filarial infectivity of persons to

mosquitoes in a community has an intimaterelation to the picture of the occurrence ofmicrofilariae in the community and can be

demonstrated by a frequency distribution ofpersons in percentage for the whole populationin a community against the microfilarial levelswhich are set up for the ranges of the expectedinfection rates of mosquitoes fed on the carriers

having adequate numbers of microfilariae toget the rates. The conception may be applicableto the infectivity of persons in a patient's

150 Yoshito WADA

house within a community. The average of the

levels is useful in comparing the pictures of theoccurrence of microfilariae among communitiesamong houses or and will be called the index of

filarial infectivity of persons to mosquitoes ina community or in a house. The index is thoughtto have a close relation to the natural infection

rate of mosquitoes in a community or in ahouse as far as mosquitoes C. pipiens group areconcerned in the transmission of filariasis.

4) A familial aggregation of carriers was

roughly detected in Nagate Village though not

significantly where the microfilarial incidence

was 14.0%, while the same phenomenon was

denied in Aogashima (Hayashi et al., 1959)

where the incidence was 12.0%. On the other

hand it was proved strongly significant in

Amakubo (Nagatomo, 1961) where the incidence

was as high as 17.2%. The above suggests that

the borderline to make possible the occurrence

of the familial aggregation of carriers in a

community may be near 15% in the incidence.

Literatures

l) Beye,軌K. &GuI孟盈n,J. : The epide-

miology and control of filariasis (Wucher^Tia

baフicrofti and Brugit一　rial叩′f)｡ WHO/Fll./26,

35ppり1961.

2) 『赫盗品R長　T.: Supplementstothefindings

on the susceptibility of Japanese mosquitoes

to w uchereriu b-crofti一1. On the susceptibility

of (二alex pip孟だfSS耶olesttis. Nagasaki Med. J,,

33 (H, Suppi.) : 71-･77, 1958. (工n Japanese

with English summary).

3) G海道io畳　　　　The transmission of Wuche-

reria hancrofti by Anopheles darli鴨i ln the

America tropics. Amer. J, Trop. Med., 28

71-85, 194臥

卑)吉頁Ry盈s鮎　S. ; Current problems

parasitological and epidemlological studies on

human and animal filarlasis in Japan｡ Nisshin一

王gaku,埠2 : 1｣2s 1955. (In Japaaese),

5) Hayash長　S. : A mathematical analysis

on the epidemiology of bancroftian and malayan

filariasis in Japan. Jap. J一Exp. Med,, 32 ;

13-43, 1962｡

6) Haya軸毒, S. ct　盈畳　: Studies on the

bancroftian filariasis in Aogashima Island of

the王zu Archipelago. Jap, J. Paras., 8 : 895-

903,柑59｡(In Japanese with English summary)｡

7) Kes畠e冨, 4,｡F. : An effective programme

for the control of filariasis in Tahiti｡ Bull. Wld

Hlth Org.s 18 : 633-664, 195ア.

8) Na卵告omo,畳. : Epidemiology and control

of bancroftian filariasis in some villages of

Nagasaki prefectureー3, Epidemiology and mass

treatment of filariasis in Amakubo village.

Endem. Dis° Bull. Nagasaki, 3 : 75-86, 1961.

9) Omori, N∴ Experimental studies on the

role of the house mosquito, Culex p岬ens

palle耶in the transmission of bancroftian

filariasis. 2. On the pattern of spatial distri-

bution of microfilarla in the peripheral blood

stream of the carrier. Nagasaki Med. J. 33

1045-1053, 195臥(In Japanese with English

summary).

柑) On　号　N. : A review of the role of

mosquitoes in the transmission of Malayan

and王∃ancroftian filariasis in Japan. Bull｡ W上d

Hlth Org., 27 : 585-594, 1962.

ll) Omori, N. e告a畳: Epidemiology of

Bancroftian filariasis in Hisamatsu Village,

Miyako工sland, the Ryukyus｡ 1, Results of a

survey made in October, 1961. Endem. Dis.

Bull. Nagasaki,埠　194-205, 1962,

12) Osh量ma, M. : Studies on the incidence

of bancroftian filariasis and the natural infec-

tion of mosquitoes in W一estern Kyushu, Japan,

1. On the incidence of filariasls. Nagasaki Med,

L, 30 : 1467-1477, J955. (In Japanese with

English summary).

13) Sasa, M. : Studies on the epidemiology

and control filariasis in Japan. Medicine of

Japan in 1959, 2: 637-643, 1959- (In Japanese),

1年) Sasa,朗. eta互. : Studies on the control

of bancroftian filarlasis in Amami Oshima

Endemleity of filariasis 151

island. Jap. J. Paras., 8 : 872叫879, 1959- (In Japanese with English summary〕.

摘　　　　　　　　要

長崎県下の長手,鐙瀬両部落で,1960年来,バンク

ロフト糸状虫症の疫学,特に伝播蚊との関係について

一連の調査研究を行なっているが,本報では主として

糸状虫症の浸淫状況について述べる.

1)長手部落:1961年8月,部落民全員577名から

採血し,81名(14.0%)の仔虫陽性者を認めた.男性

の仔虫陽性率は女性よりも有意的に高い.陽性率は5

-9才では低く,年令が進むにつれて高くなり,40-

49才及び50-59才で最高となって,その後又低くな

る.症状保有者は全住民の10.3%であり,最も普通な

症状はクサフルイで,20-29才から見られ,乳び尿及

び陰のう水腫はこれに比べるとかなり少なく,よりお

そくから初発する.

糸状虫症浸淫の歴史的変遷を解明するために,仔虫

及び症状の存否を組合わせた4つの症状区分につい

て,それらに属する人員構成を吟味して次のような推

定を得た.1)部落民の約40%以上の者が一生の間に

感染を受ける.2)支那事変勃発以前の約50年の間に

はかなり盛な感染が起っていたと考えられる.3)支

那事変及び第二次世界大戦の約8年間には感染の強さ

がかなり弱くなり,4)終戦後再びかなり強い感染が

起ったように思われる.

アカイエカの好適発生源が多数存在する部落東部

に,患家が比較的集中的に分布している.

平均仔虫数は,若,中年令層に高い傾向がみられる

が,散発的には重感染を受けたと思われる者が年令,

性に関係なく見られる.

1961年10月から1963年5月までの約19カ月の間,低

温時における吸血活動の停止と,引き続く伝播蚊の駆

除のために感染は起らず,又起さなかったが,この間

に,約14%の仔虫陽性者が自然陰転した.

2)鐙瀬部落: 本部落はトウゴウヤプカの好適発生

水域が驚くほど多数に存在する岩礁海岸にある.殆ん

どの家は,第二次世界大戦中及び戦後の数年間に,近

隣部落からの移住者によって建てられた. 1961年,部

落全員84名を採血し,7名(8.3%)の仔虫陽性著を

認めた.若い年令層に仔虫陽性者が極めて少ないの

で,移住後の部落内での感染は極めて少なかったよう

に思われる.成人の陽性者は移住前の感染者であろ

う.こゝに,多発するトウゴウヤプカの伝播性が問題

となるが,この事については後報する.

3)ある集団内(又は患家内)に於ける住民の,蚊

への感染能力段階に対する頻度分布は,被吸血者の仔

虫数から推定される蚊の実験的感染率の5段階の仔虫

数水準に属する人員の百分率頻度分布によってよく示

し得る.この頻度分布は,その集団(又は患家)の対

仔虫密度仔虫保有率の分布と密接な関係があるのであ

るが,その水準の平均,即ち平均感染能力を,集団

(又は患家)の感染能力指数と名づける.この指数

は,部落(又は患家)におけるアカイエカの自然感染

率と密接な関係があると思われ,集団(又は患家)に

於ける仔虫保有相とアカイエカ群の自然感染との関係

を究明していくのに役立つと考えられる.

4)仔虫陽性者の家族集積性は,仔虫陽性率が14.0

%であった本部落ではその傾向があるが有意的ではな

く,林ら(1959)は12.0%の青カ島ではこれが認めら

れなかったと云って居り,永友(1961)は17.2%の天

久保部落で高度にこれを認めている.これらの事か

ら,家族集積性が認められる仔虫陽性率の限界は15%

前後にあると考えられる.

Received for publication September 10, 1963